Chest compression monitoring during the course of CPR is now possible with the Real CPR Help® and CPR-D-padz technology marketed by ZOLL Medical Corporation. This technology is described in U.S. Pat. Nos. 6,390,996, 7,108,665, and 7,429,250, and includes the use of an accelerometer to measure accelerations of the chest and calculating the depth of each compression from the acceleration signal. The technology is used in ZOLL's Real CPR Help® compression depth monitoring system to provide real-time rate and depth CPR feedback for manual CPR providers. Commercially, it is implemented in ZOLL's electrode pads, such as the CPR-D•Padz® electrode pads. It is also implemented for training use in the PocketCPR® chest compression monitor and PocketCPR® iPhone app.
U.S. Pat. No. 6,390,996 to Halperin, as well as U.S. Pat. No. 7,122,014 to Palazzolo, described chest compression monitors capable of determining chest compression depth accurately during repeated rapid chest compressions required by CPR. The devices of Halperin and Palazzolo were adapted to be placed between the CPR provider's hand and the patient's sternum during CPR. In both cases, the CPR chest compression monitor is held in fixed relationship to the chest during use, and the chest compression module is operable to determine the depth of each chest compression based on acceleration data from accelerometers in the chest compression module, without input from other sources, especially without input of data from other sensors fixed in space or remote from the compression module. The disclosures of U.S. Pat. Nos. 6,390,996, 7,108,665, and 7,429,250 to Halperin, and U.S. Pat. No. 7,122,014 to Palazzolo are hereby incorporated by reference.
Various other chest compression monitors have required or suggested the use of additional inputs to detect the initiation of a compression. Myklebust et al., System for Measuring and Using Parameters During Chest Compression in a Life-Saving Situation or a Practice Situation and Also Application Thereof, U.S. Pat. No. 6,306,107 (Oct. 23, 2001) describes a device which uses a pressure pad containing an accelerometer and requires a force activated switch to determine the start of each compression in order to determine the depth of depressions. However, Myklebust does not provide a means to measure compression depth using an accelerometer alone, nor does Myklebust account for some kinds of error in the measured value of chest compression depth (such as drift). Our own prior patent, Palazzolo, et al., Method of Determining Depth of Compressions During CPR, U.S. Pat. No. 7,122,014 (Oct. 17, 2006) after describing methods of determining compression depth with such additional inputs, also describes the use of switches to detect the start of compressions that may be beneficial in discriminating between acceleration due to chest compressions and external acceleration of the patient.